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Help with a tone arm problem

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Posted on February 16, 2021 at 13:22:12
MylesJ
Audiophile

Posts: 1150
Location: Oregon Coast
Joined: October 25, 2001
I have a Kenwood 770D table with a tone arm made by Jelco for Kenwood. After changing headshells and VTA heights twice there is some resistance to horizontal movement of the arm, enough to cause the record to skip backwards after two revolutions. This arm is common on the later Kenwood DD tables. They have High Stability printed on the block with the jewel pivots.

I presume that a piece of grit found its way in between the vertical post and the shell it goes through. The only remedy I can think of is to de-solder the internal fine wiring and disassemble it to clean it. Any other ideas to try before I go that far?

 

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RE: Help with a tone arm problem, posted on February 16, 2021 at 13:44:28
John Elison
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Posts: 23077
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since:
January 29, 2004
I wonder if the arm lifting mechanism is touching the tonearm as it plays. Cut a strip of paper and try to slip in in-between the arm and the lift to make sure they aren't touching when a record is playing. This problem can sometimes result from raising the arm height to change VTA.

Good luck,
John Elison

 

RE: Help with a tone arm problem, posted on February 16, 2021 at 14:17:31
MylesJ
Audiophile

Posts: 1150
Location: Oregon Coast
Joined: October 25, 2001
John - I can see light between the arm and the lift. If I hold the arm up a bit higher there is still some resistance. If I set the counterbalance so the arm floats freely and give it a horizontal tap it only goes a little bit
instead of a couple of inches.

 

Does that deck have automatic arm return?, posted on February 16, 2021 at 14:20:34
ghost of olddude55
Audiophile

Posts: 15957
Joined: July 14, 2017
You might have bad grease on the auto return mechanism. Old grease will turn into a glue-like paste with age.

The problem is not that there is evil in the world, the problem is that there is good. Because otherwise, who would care?

 

RE: Help with a tone arm problem, posted on February 16, 2021 at 14:21:52
PAR
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Posts: 1466
Location: South London, UK
Joined: June 4, 2019
Contributor
  Since:
June 4, 2019
MylesJ, John Elison is almost certainly correct. If trying to slip paper in between does not work for you then just get your eye level with the gap (or what should be a gap) between the arm tube and the arm lowering platform as it traverses the disc. I expect that at some point the two will meet causing a jump.

The obvious solution is to lower the arm lifting platform by a small amount so that it does not touch the arm tube when lowered but still provides a suitable amount of elevation to allow cueing.


"We need less, but better" - Dieter Rams

 

RE: Help with a tone arm problem, posted on February 16, 2021 at 14:44:26
PAR
Audiophile

Posts: 1466
Location: South London, UK
Joined: June 4, 2019
Contributor
  Since:
June 4, 2019
MylesJ, thanks for the further information. Can you reverse the change that you made and see if the problem remains? It is starting to sound like a bearing issue, either the bearing itself or the lead out wires binding.

As far as I can tell from the user manual there is no automation of the arm.

"We need less, but better" - Dieter Rams

 

RE: Help with a tone arm problem, posted on February 16, 2021 at 16:28:12
MylesJ
Audiophile

Posts: 1150
Location: Oregon Coast
Joined: October 25, 2001
PAR - I put on a different headshell that sat too low. I had to raise VTA to the maximum to clear the record. It wasn't high enough to sound good so I put back the other headshell and dropped the adjuster to the height it was before I made the change. I think I may have raised it too high which caused the problem.

Some of those arms have a manual lever for raising the arm and some have a sensor like the 770D that kills the power to the magnet that pushes up on the lift bar from under the plinth. It is spring loaded in the up position. You can't lower the tone arm if the power is not on. That raise/lower function still works properly.

 

RE: Help with a tone arm problem, posted on February 17, 2021 at 04:00:28
PAR
Audiophile

Posts: 1466
Location: South London, UK
Joined: June 4, 2019
Contributor
  Since:
June 4, 2019
" PAR - I put on a different headshell that sat too low. I had to raise VTA to the maximum to clear the record. It wasn't high enough to sound good so I put back the other headshell and dropped the adjuster to the height it was before I made the change. I think I may have raised it too high which caused the problem."

So I understand from this that the problem was a physically incompatible headshell and therefore assume that the issue has now been fixed.

"We need less, but better" - Dieter Rams

 

RE: Help with a tone arm problem, posted on February 17, 2021 at 12:52:13
MylesJ
Audiophile

Posts: 1150
Location: Oregon Coast
Joined: October 25, 2001
PAR - no, the horizontal resistance still happens with the original head shell. Not much horizontal resistance to moving the arm manually but enough that the arm cannot move it before it skips backward.

 

RE: Does that deck have automatic arm return?, posted on February 17, 2021 at 12:54:05
MylesJ
Audiophile

Posts: 1150
Location: Oregon Coast
Joined: October 25, 2001
olddude - the automatic function only raises the arm, it does not move the arm horizontally

 

Arghh...., posted on February 17, 2021 at 14:00:55
ghost of olddude55
Audiophile

Posts: 15957
Joined: July 14, 2017
I had a KD-50F, which also had a Jelco arm, very briefly maybe 15 years ago. Could't remember if it had auto return, so I took a shot.
The Vinyl Engine has a repair/service manual for your KD-770D. You have to create an account in order to see it, but it's free.

The problem is not that there is evil in the world, the problem is that there is good. Because otherwise, who would care?

 

I tried to google Jelco tonearm lubrication, and it was a bust. The , posted on February 18, 2021 at 16:53:44
alaskahiatt
Audiophile

Posts: 5804
Joined: December 9, 2000
Contributor
  Since:
November 1, 2005
lubrication of the horizontal bearing in tonearms had totally opposite responses. They all say to clean first, but they disagreed about lubricating or leaving dry.

I did see the one link below, but I didn't take time to study it.

Seems like you tried everything else.

 

I fixed the problem, posted on February 23, 2021 at 23:06:09
MylesJ
Audiophile

Posts: 1150
Location: Oregon Coast
Joined: October 25, 2001
After trying everything you guys suggested I took the tone arm off and disassembled it. I found that the grub screw that positions the vertical bearings had gotten loose. The bearing was not held against anything and the screw was out far enough to engage the inner wall of the tone arm base. I tightened it up and that was the end of the problem. Thanks for all the suggestions.

 

Boy, that's not in the emergency checklist. Relief! nt, posted on February 26, 2021 at 18:42:42
alaskahiatt
Audiophile

Posts: 5804
Joined: December 9, 2000
Contributor
  Since:
November 1, 2005
nt

 

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